Posterosuperior view of right cerebellopontine angle. The trigeminal nerve (CN V) emerges from the lateral pons and the trigeminal ganglion is located deep to the dura mater in Meckel’s cave. The facial (CN VII) and vestibulocochlear (CN VIII) nerves emerge from the lateral pontomedullary junction and can be seen entering the internal acoustic meatus. The anterior inferior cerebellar artery (AICA) arises from the basilar artery and passes between CNs VII and VIII. The labyrinthine artery most commonly branches from AICA and accompanies CN VIII to the inner ear. The subarcuate artery, also a branch of AICA, supplies the bony labyrinth, facial canal, and mastoid antrum. The posterior inferior cerebellar artery (PICA) arises from the vertebral artery and passes between vagus (CN X) and spinal accessory (CN XI) nerves before they enter the jugular foramen. The superior petrosal vein (vein of Dandy) is an important venous drainage system in the posterior fossa. It drains the anterior cerebellum and brainstem and forms usually by union of the pontine trigeminal vein, vein of the cerebellopontine fissure, and the vein of the middle cerebellar peduncle. Some of the choroid plexus of the fourth ventricle can be seen along with the foramen of Luschka, which communicates this ventricle with the subarachnoid space of the cerebellopontine cistern.  (Image courtesy of AL Rhoton, Jr.)